Accession Number:

ADA193193

Title:

Enantioselective Ring-Cleavage of meso- Epoxides with beta-Halodiisopinocampheylboranes.

Descriptive Note:

Technical rept.,

Corporate Author:

PURDUE UNIV LAFAYETTE IN

Personal Author(s):

• Joshi, N. N.r
• Srebnik, M.
• Brown, Herbert C.

Report Date:

1988-04-26

Pagination or Media Count:

11.0

Abstract:

B-Halodiisopinocampheylboranes, IpcBX, in particular the bromide 1b, and the Iodide 1c, differentiate between the enantiotopic carbon-oxygen bonds of meso-epoxides to furnish 1,2-halohydrins of moderate to excellent enantiomeric purity. Thus --1R, 2R-2-bromocyclohexanol, --1R, 2R-2-iodocyclohexanol, --1R, 2R-2-iodocyclohex-4-en-1-o1 and --1R, 2R-2-bromocyclohex-4-en-1-o1 are obtained in 84, 91, 63 and 95 ee respectively from the corresponding meso-epoxides and haloborane reagents. Simple recrystallization from pentane then gives halohydrins of essentially 100 ee cis-2-butene oxide and cis-3-hexene oxide furnish the corresponding 1R, 2R-iodohydrins in 78 and 69 ee respectively. In all cases the S carbon of the meso-epoxide is selectively cleaved. This is the first example of enantioselective ring cleavage of meso-epoxides to obtain optically active 1,2-halohydrins. Keywords Asymmetric synthesis.

Descriptors:

• *EPOXY COMPOUNDS
• *HALOHYDRINS
• *SYNTHESIS
• *BORANES
• ASYMMETRY
• CARBON
• RECRYSTALLIZATION
• CHEMICAL BONDS
• CLEAVAGE
• CYCLIC COMPOUNDS
• OXYGEN
• STEREOCHEMISTRY

Subject Categories:

• Organic Chemistry
• Physical Chemistry

Distribution Statement:

APPROVED FOR PUBLIC RELEASE